1. Field of the Invention
The invention relates to a rotor for a rotary electric machine, and more particularly to a rotor for a rotary electric machine in which a plurality of permanent magnets are buried, at intervals in a circumferential direction, in the outer peripheral interior of a rotor core.
2. Description of Related Art
For example, Japanese Patent Application Publication No. 2009-124899 (JP-A-2009-124899) discloses a rotary electric machine 60 provided with a stator 602, at an inner periphery portion of which a stator coil is wound, and a rotor 62, of buried permanent magnet type, rotatably provided in the stator 602. The rotor 62 is made up of a rotary shaft (not shown) and a cylindrical rotor core 612 fixed thereto.
The above rotor core 612 is integrally constructed by crimping or the like after stacking magnetic steel sheets in the axial direction, each magnetic steel sheet being formed through punching into a circular ring-like shape. A plurality of magnetic poles are provided, equally spaced in the circumferential direction, on the outer periphery of the rotor core 612. FIG. 6 illustrates one magnetic pole in a state viewed from an axial-direction end face in an enlarged manner. FIG. 6 illustrates one magnetic pole 624, together with part of the stator 602, from among the members that are disposed evenly spaced (45°-angle intervals such that the central axis of a rotary shaft is the center of each fan shape) on the outer periphery of the rotor core 612 of the rotor 62.
A plurality of teeth 603 that point inwards in a radial direction are provided, at equal spacings in a circumferential direction, on the inner periphery of the stator 602. Slots 604 are respectively formed, in a number identical to that of the teeth 603, between mutually adjacent teeth, such that the slots 604 are opened on the inner periphery side and at both end portions in the axial direction. A stator coil (not shown) that is wound around the teeth 603 is inserted into the slots 604. As a result, a rotating magnetic field that rotationally drives the rotor 62 is formed inwards of the stator 602 when the stator coil is energized.
Each magnetic pole 624 provided in the rotor core 612 has a pair of permanent magnets 626, disposed so that a mutual spacing widens towards an outer peripheral face 613, and a magnetic flux suppression hole 628 that is formed, on the inward side in the radial direction, between inner-periphery-side end portions of the permanent magnet 626. The magnetic flux suppression hole 628 is made up of three holes 628a, 628b. Two end holes 628a having substantially triangular shapes are formed each communicating with a respective magnet insertion hole 632 through which there is inserted a respective permanent magnet 626 having an end face shape (and cross-section shape) that is an elongated rectangular shape. A substantially rectangular central hole 628b is formed between the two end holes 628a with bridge portions 636 interposed therebetween, which are thin core regions. The outer-periphery-side end portions of the three holes 628a, 628b are formed so as to run along an imaginary straight line that passes through the corners (or end portions), on the inward side of the circumferential direction, of the pair of permanent magnets 626.
Herein, the above publication indicates that, in the rotary electric machine 60 provided with the rotor 62 having such magnetic poles 624, reluctance torque is enhanced as a result of an increase of the difference between q-axis inductance Lq and d-axis inductance Ld in the magnetic poles 624, by forming the magnetic pole suppression hole 628 having a void in the center, on the inward side in the radial direction, in each magnetic pole 624.
In the magnetic poles 624 of the rotor 62 of JP-A-2009-124899, there is formed, as a magnetic path region 638, a core portion that is surrounded, on three sides, by the pair of permanent magnets 626 and the magnetic flux suppression hole 628. In the magnetic path region 638, however, the vicinity of the outer-periphery-side end portion of the central hole 628b is a region in which there flows hardly any magnet magnetic flux from the permanent magnet 626, or q-axis magnetic flux (dotted line in FIG. 6) that flows from the teeth 603 of the stator 602 through the rotor core 612. There is thus room for improvement in terms of utilizing this region more effectively.